Ground level transformer unit

ABSTRACT

A transformer unit comprising a transformer, a ground level base pad having a vertical cable opening therethrough, and an open top, open bottom vertical cable vault situated in the earth, the upper end thereof being received in the pad opening to provide easy access to and training room for underground electrical cables connected to the transformer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention lies in the field of ground level mounted transformers.It is particularly related to means to provide easy access and greatertraining room for electrical cables connected to a ground level mountedtransformer and to provide protection against damage to cables duringsite construction.

2. Prior Art

Ground level transformers are commonly mounted on pads. Generally thetransformer pads have an opening to receive underground electricalconductors or cables therethrough to connect to the transformer. Whencables protrude from the ground and through the opening in a pad, littlevertical space is available for maneuvering of the cables. Also, afterthe cables have been installed in the earth and before a transformer isplaced in position, great possibilities exist for vandalism oraccidental damage to the cables during site construction.

An additional problem with transformers mounted on ground level pads isthat during cold weather, ground freezing causes the pads to be pushedupwardly, sometimes referred to as frost heave. If cables fromunderground are tautly connected to a transformer, the upward movementof the pad and transformer can snap off the porcelain insulators towhich the cables are connected.

Examples of transformer pads for ground level mounted transformers aredisclosed in U.S. Pat. Nos. 4,050,659; 3,962,660; 3,841,032; and4,056,251.

SUMMARY OF THE INVENTION

The present invention provides means to overcome the foregoingdisadvantages. It is an object of the invention to provide thecombination of a transformer, a pad, and a housing or vault forelectrical cables to be connected to the transformer, thereby providingeasy access to the cables and greater training room therefor.

Another important object of the present invention is to protectelectrical cables, once they are situated at a transformer site, againstvandalism and accidental damage before the transformer base pad andtransformer are placed in position.

The invention comprises a vault used in conjunction with a transformerpad and ground level transformer, the transformer pad having an openingtherethrough to receive underground electrical cables, the vault beingsituated below the ground level and comprising a hollow, open top, openbottom rigid structure. The upper end of the cable vault is dimensionedto be received in the transformer pad opening. The lower end of thecable vault may be straight or it may be canted at an angle with respectto a vertical plane to facilitate entry of cables.

The upper end of the cable vault may be provided with a removable cover.The cover is removed when a transformer pad and the transformer areplaced in position over the vault, but serves to protect cables in thevault until the transformer and pad are installed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages together with the function of theinvention may be better understood by reference to the followingdetailed description and the drawings, wherein:

FIG. 1 is a perspective view, shown partially cutaway, of a unit,including the transformer, the pad, and the cable vault, embodying thepresent invention in an operative environment.

FIG. 2 is a perspective view of a cable vault of the present inventionsecured in position in the earth and showing how the cover ispositioned.

FIG. 3 is a side elevational view, partly sectional, illustrating theconfiguration of one embodiment of a cable vault.

FIG. 4 is a sectional view taken along A--A of FIG. 3.

FIG. 5 is a frontal elevational view, partly in section, of the cablevault.

FIG. 6 is a cross-sectional view of a transformer mounted on atransformer pad on the earth's surface and showing a cable vault inwhich the upper end extends above the top surface of the pad.

FIG. 7 is an elevational view of another embodiment of a cable vault.

FIG. 8 is a cross-sectional view taken along the line 8--8 of FIG. 7.

FIG. 9 is a top view of the embodiment of FIGS. 7 and 8.

DETAILED DESCRIPTION

Referring to the drawings and particularly to FIG. 1, referencecharacter 10 generally indicates a cable vault positioned in the earthand mostly below the ground level 12. A transformer pad 13 is situatedabove the cable vault 10, the transformer pad having an opening 14therethrough to receive the upper portion of the cable vault. Atransformer 15 rests on top of the transformer pad 13. A cover 16 ishinged to the transformer 15 and covers the conductors connected to thetransformer. In some cases cover 16 may not be hinged but may be slid upand down into and out of position.

The cable vault 10 comprises an upright hollow body having an upper openupper end 22, and open lower end 24, a front 26, a rear 28, and sides 30(see FIGS. 2, 3, and 4). The lower end 24 is canted from the front 26 tothe rear 28, at an angle, preferably 45 degrees, with respect to avertical plane, or to the plane of the front portion 26. Undergroundcables 18 enter the cable vault 10 at the lower end 24 of the frontportion 26, and it will be apparent that the canted configuration of end24 facilitates the entry of the cables 18 into the cable vault.

An outwardly projecting ridge 32 (see FIG. 3) is provided at the loweredge of the front 26. Similarly, a ridge 34 is provided along the lengthof the lower end of the rear portion 28. The ridges 32 and 34 provideanchoring means to better secure the cable vault 10 when it is inposition below the ground surface 12 and as reinforcing to stiffen thecable vault to thereby better enable it to resist collapse as dirt iscompacted around it.

The upper end of the cable vault 10 is dimensioned to be received in thetransformer pad opening 14. This is accomplished as shown in FIG. 2 byproviding an upwardly projecting collar 36, properly dimensioned to fitin the transformer pad opening 14. The collar 36 is formed by ahorizontal upwardly extension of the upper portions of the front 26,rear 28, and sides 30.

A cover 40 (see FIGS. 2, 3, and 5) is dimensioned to receive the upperend of collar 36. Tamper-proof means are provided on the cover member 40to attach it to the upper end of the vault. The illustrated tamper-proofmeans is a bolt having a pentagonal head received in a tubularintegrally extending boss 43. Bolt 42 thus requires a special socket toremove it and to thereby remove lid 40.

When the cable vault 10 is positioned in place in the earth at the siteof a transformer location, the collar 40 protrudes upwardly above theearth's surface. Incoming cable ends 18 are housed within the cablevault 10, and the cover member 40 provides protection against vandalismor accidental damage to the cables. The cover member 40 is removed whenthe transformer pad 13 and the transformer 15 are placed in position.

The cable vault is preferably made of lightweight, non-conductionmaterial, such as plastic or fiberglass. To increase the strength of thecable vault 10 and prevent collapse after it is positioned in the earth,a plurality of strengthening ribs 44 are provided on the front 26, rear28, sides 30. The strengthening ribs 44 are made by outwardly deformingportions of the cable vault 10. The position of the strengthening ribs44 may vary. As shown in FIGS. 2 and 5, horizontal ribs are employed onthe front portion 26 and the rear portion 28; a combination ofhorizontal and vertical ribs are employed on the sides 30.

The cable vault 10 may be provided with additional strengtheningdevices. FIGS. 3, 4, and 5 show the use of metallic rods 46, each formedas a rectangular loop having outer dimensions slightly greater than thenormal inner dimensions of the cable vault 10, but less than thedimensions of ribs 44. Upper rectangular loop 47 is positioned in theinterior of the collar portion 36 and is retained in position byintegral inwardly extending bosses 48.

FIG. 6 is a cross-sectional view of a transformer pad, transformer andcable vault mounted in position. The length of the vault collar portion36 which extends upwardly and is received in the opening 22 intransformer pad 13 is greater than the thickness of the pad so that aportion 36A extends well above the transformer pad upper surface 13A.The upwardly extending vault collar portion 36A serves to restricttampering by items that might be forced under the lower edge of thetransformer 15 or transformer cover 16.

Referring to FIGS. 7, 8, and 9, an alternate embodiment of the cablevault is illustrated. In this arrangement the cable vault is circular inplanes taken perpendicular the vertical axis or the vault may be said tobe of truncated conical configuration. The circular configuration hasthe advantage that it is inherently stronger than a rectangularcross-sectioned configuration, and therefore, can be more easilyconstructed of sufficient strength to resist collapse without the use ofreinforcing bars as has been previously described with the rectangularcross-sectioned vault of FIGS. 1-5.

The circular cross-section vault of FIGS. 7, 8, and 9 includes a taperedbody portion 50 and an integral upper upwardly extending collar portion52 which preferably is of rectangular cross-section to conform with thepreferred configuration of opening 22 in the transformer pad. It can beunderstood that this collar 52 may be of square or any otherconfiguration as long as it is received within the opening provided inthe transformer pad. Preferably, the mating of the opening in thetransformer pad and the upwardly extending collar portion 52 is of asnug arrangement, that is, one which easily permits the transformer padto be assembled down over the collar of the cable vault but whichachieves a substantially continuous contact around the full exteriorperiphery of the vault opening.

The upwardly extending collar portion 52 has an opening 54 thereinthrough which cables pass to be connected to the transformer above thetop surface of the transformer pad. The lower end of the body 50 mayinclude an intergral outwardly extending lip 56 as a reinforcing andanchor means.

APPLICATION OF THE INVENTION

The invention is directed to the combination of a ground mountedtransformer, a transformer pad, and a cable vault. These three elementsare ideally arranged for a residential and industrial subdivision inwhich electrical power is supplied by underground cables. In the UnitedStates and many foreign countries, it is becoming more prevalent forpower companies to install electrical service underground because of theimproved appearance of neighborhoods achieved by eliminating theunsightly poles, pole-mounted transformers and overhead conductors whichhave been most commonly employed in the past.

In a typical installation of a subdivision in which undergroundelectrical cables are to be utilized, before constructing houses, theprimary electrical distribution system is installed. Trenches are dug,and cables are laid in the ground. Where a transformer is required, inthe past it has been the custom to merely extend the cables above theground and cut them off, leaving the exposed cables above the earth'ssurface. This results in the possibility of damage to the cable ends andto hazard to workmen. The present invention overcomes these problems byproviding a cable vault which is mounted in the earth's surface at thetime the cables are installed. The cables may extend in the vault andmay be curled or coiled within the vault to leave sufficient length ofcable to later extend upwardly for connection to a transformer. All ofthe cable vault is buried beneath the earth's surface except theupwardly extending collar portion and cover which is usually surfacemounted and it is not necessary that any portion of the cable normallyextend above this upper end of the vault until it is time to install thetransformer pad and transformer. To further protect the cables withinthe cable vault and to prevent the cable vault from being inadvertentlyfilled with dirt, the removable cover 40 as previously discussed andillustrated in FIGS. 2, 3, and 4 may be attached.

When it is time to install the transformer, the workmen merely removethe cover 40 and position a transformer pad on the earth's surface withthe upwardly extending collar portion 36 of the vault received withinthe opening in the pad. In many instances, transformers for use inunderground distribution systems, are shipped from the factory with thetransformer attached to the pad. The workmen open cover 16, exposing thepart of the transformer where electrical connections are made. Theworkmen then may reach down into the interior of the vault 10 and pullthe ends of the cables 18 upwardly and attach them to the transformer.While only four cables are shown, the number is usually greater as inmost instances, the primary cables feeding the transformer are looped,providing two sets of feeder cables plus the secondary conductors. Thecables are connected to porcelain insulators 58 or to high voltage deadfront elbows extending from transformer 15. It can be seen that if cable18 extends tautly from the earth and pad 13 is pushed upwardly by frostheave, then insulators 58 can be snapped off, interrupting powerservice. With the use of cable vault 10, slack can be employed in thecables 18 as they are connected, allowing for shifting of the pad andtransformer.

Thus, the transformer, the transformer pad, and the cable vault becomean integrated unit providing improved installation of undergroundelectrical distribution systems with improved safety and with thedecreased possibility that damage can occur to the exposed cables afterthey are buried underground, both before the transformer is installedand after it is connected to the underground cables.

While the invention has been described with a certain degree ofparticularity, it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure. It is understoodthat the invention is not limited to the embodiment set forth herein forpurposes of exemplification, but is to be limited only by the scope ofthe attached claim or claims, including the full range of equivalency towhich each element thereof is entitled.

What is claimed is:
 1. A ground level transformer unit for connection tounderground cables, including:a horizontal pad having an upper and alower surface, the lower surface being adapted to rest upon the earth,and the upper surface adapted to receive a transformer thereon, the padhaving a vertical cable opening providing means to receive undergroundcables therethrough; and a transformer positioned on said pad havingmeans for connection to underground cable extending through said cableopening, the improvement comprising: a cable vault of vertical, hollow,open-top and open-bottom construction, and of cross-sectional dimensionsto receive underground cables therethrough while providing space toaccept slack in the cables, the cable vault having an upper shoulderportion of dimensions less than the dimension of said pad cable openingand the shoulder portion being slidably received in said pad cableopening permitting relative vertical movement between said pad and thecable vault.
 2. A transformer unit as in claim 1 including a pluralityof integral horizontal ribs formed in the walls of said cable vault. 3.A transformer unit as in claim 1 including a plurality of reinforcingloops disposed within said cable vault.
 4. A transformer unit accordingto claim 1 wherein said cable vault shoulder received within said padopening is of sufficient vertical length so that the upper end thereofis above said pad top surface, the upper extending shoulder serving toresist tampering with cables extending through said cable vault and padopening. .Iadd.
 5. A ground level transformer unit for connecting tounderground cables, comprising:a horizontal pad having an upper and alower surface, the lower surface being adapted to rest upon the earthand the upper surface adapted to receive a transformer thereon, the padhaving a vertical opening providing means to receive underground cablestherethrough; a transformer positioned on said pad having means forconnection to underground cable extending through said cable opening;and a cable vault of vertical, hollow, open-top and open-bottomconstruction, and of cross-sectional dimensions, in a plane parallel tosaid upper and lower surfaces, greater than said pad cable opening andless than said pad, the vault adapted for burial beneath the earth'ssurface and to receive underground cables therethrough while providingspace to accept slack in the cables, the cable vault having an open topportion configured to communicate with said pad cable opening, the cablevault top portion being in contiguous relationship with said pad lowersurface, providing a passageway for slacked underground cables toconnect to said transformer. .Iaddend.